JP3205371B2 - Manufacturing method of fluoride thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluoride thin film, and more particularly to a method for producing an optically uniform fluoride thin film such as a fluoride glass thin film and a barium fluoride thin film.

[0002]

2. Description of the Related Art Fluoride glass has excellent transmission characteristics in the infrared wavelength region, and is attracting attention as a material having a high possibility of realizing an extremely low loss optical fiber in the infrared wavelength region. As such a material, 52 mol% of ZrF ₄ , 24
ZBN glass consisting of mol% BaF ₂ and 20 mol% NaF
(Including 4 mol% of AlF ₃ ), and La
Etc. are added (ZBLAN glass). Conventionally, when manufacturing such a fluoride glass, a melting method of a solid phase raw material batch has been used. That is, the solid raw material is weighed, pulverized,
After mixing, the raw materials are melted in batches and quenched in a crucible to produce a fluoride glass. For this reason, when each raw material is weighed, pulverized, and mixed, transition metal impurities such as Fe, Ni, Cr, and Co, which absorb in the infrared wavelength region, are mixed, and water that causes oxide scatterers is removed. There is a problem that adsorption is likely to occur. Further, there is a drawback that when melting the glass, impurities are mixed due to corrosion of the crucible wall.

On the other hand, barium fluoride (BaF ₂ ) can be applied as an optical material for windows, prisms, lenses, etc.
It is known that it is effective as a buffer layer when growing a compound semiconductor thin film on a silicon substrate. In addition, since a barium fluoride thin film is grown on a silicon substrate to a thickness of the order of 10 μm, and a rare earth element is doped into the thin film, an optical amplification effect occurs, so that it is expected to be applied to optical integrated circuits in the future. I have. As a method for producing such a barium fluoride thin film, conventionally, molecular beam epitaxy (MBE) has been applied, but the growth rate is not fast (about 1 μm / hr), and the crystal integrity is not sufficient. And poor doping efficiency.

[0004]

As a method for solving such a problem, attention has been paid to a chemical vapor deposition (CVD) method. The CVD method has the following advantages: (1) a large area and a uniform thin film can be obtained; (2) a high growth rate; and (3) easy composition control. However, in order to apply the CVD method, a CVD raw material having a high vapor pressure is required, but no suitable raw material has been found for barium. That is, a conventionally known β-diketone complex bis (dipivaloyl methanate) barium [Ba (dpm)
₂ ], bis (hexafluoroacetylacetonato) barium [Ba (hfa) ₂ ], bis (trifluoroacetylacetonato) barium [Ba (tfa) ₂ ], bis (dimethylheptafluorooctane dionato) barium [Ba ( fod) ₂ ] has a vaporization temperature of 2
The temperature was as high as 20 to 260 ° C., and the heated compound was thermally decomposed in the container and deteriorated, and there was a problem that the vaporization gradually decreased during repeated use.

An object of the present invention is to provide a method for producing an optically uniform thin film of fluoride for use in an optical fiber or an optical element by solving the problems of the prior art.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to set a predetermined base material in a gas phase reaction vessel, introduce a compound containing barium and other elements in a gas phase, and decompose the compound in a plasma atmosphere. Then, in the method of providing a fluoride thin film on the substrate, in the barium-β-diketone complex represented by the following formula as a compound containing barium (provided that the combination of (R ₁ , R ₂ ) in the following formula is ( _{CF 3, C 2 F 5)} , (CF 3, C 3 F 7), (C 2
_{F 5, C 2 F 5)} , (C 2 F 5, C 3 F 7), (C 3 F 7, C 3 F 7), (C 3 F 7, C 4 F
₉ )), or a predetermined base material is placed in a gas phase reaction vessel, and a compound containing barium and a reactive gas, if necessary, are introduced in a gas phase, and this is thermally decomposed. In the method of providing barium fluoride on the base material, the barium compound represented by the following formula as a compound containing barium-
β-diketone complex (however, the combination of (R ₁ , R ₂ ) in the following formula is (CF ₃ , C ₂ F ₅ ), (CF ₃ , C ₃ F ₇ ), (C ₂ F ₅ , C ₂ F ₅₎ ), (C
₂ F ₅ , C ₃ F ₇ ), (C ₃ F ₇ , C ₃ F ₇ ), (C ₃ F ₇ , C ₄ F ₉ )), and further, in the above two methods, the barium This can be achieved by introducing a rare earth element β-diketone complex together with a -β-diketone complex in a gas phase, and incorporating the rare earth element in the barium fluoride thin film.

[0007]

Embedded image

The rare earth elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (N
d), promethium (Pm), samarium (Sm), europium
(Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium
(Tm), ytterbium (Yb), lutetium (Lu) and the like. As the β-diketone ligand which is a ligand, various compounds shown in Table 1 below can be used. In the case of a rare earth element, unlike in the case of barium, a complex that can be stably vaporized can be obtained regardless of the ligand.

[0009]

The features of the method of the present invention will be described in some detail in comparison with the prior art.

First, JP-A-57-118002 describes that
A method for producing oxides by chemical vapor deposition is described, and the use of fluorinated β-diketone complexes is described. However, the kind of the ligand is hexafluoroacetylacetonate (hfa), and there is no description about the barium element.

Also, Japanese Patent Application Laid-Open No. 58-018392 discloses that
Complexes of copper or silver with fluorinated diketonates and unsaturated hydrocarbons have been described, and fluorinated β-diketone complexes have been used. However, the metal species used are copper and silver, and the ligands of the present invention are not described.

JP-A-59-070635 (US Pat. No. 418,216) describes a cerium complex compound and a method for producing the same, and describes a fluorinated β-diketone complex of cerium element. . However, there is no description about the barium element, and the ligand species used is only for dimethylheptafluorooctane dionato (fod).

Further, Japanese Patent Application Laid-Open No. 59-131537 (US Pat. No. 4,181,215) describes a method for producing a glass or ceramic article by a gas phase oxidation method, and discloses a method for producing a β-fluoride.
There is a description of diketone. However, there is no description about the barium element.

JP-A-59-139339 (West German Patent P3301225.3) describes a method for producing an anhydrous fluorine-containing 1,3-diketonate-metal complex compound, and discloses a fluorinated β-dketonate.
There is a description of diketone complexes. However, there is no description about the barium complex in this case.

Further, Japanese Patent Application Laid-Open No. 62-502748 (US Pat. No. 740680) discloses that a fluorinated β-diketone complex is used as a method for introducing a dopant into an optical fiber preform. However, the metal element is limited to europium, and there is no description about the barium complex.

Furthermore, JP-A-3-115245 (Dutch Patent No. 89901507) describes volatile organic barium compounds, in which a fluorinated β-diketone complex of barium and its adducts are described. There is a description of the compound. However, the type of ligand is limited to hfa and fod, which is completely different from that of the present invention.

As described above, in the prior art, the β-diketone complex of barium used in the method of the present invention cannot be found. Further, the complex used in the method of the present invention cannot be easily inferred from the existing complex. That is, the barium complex used in the method of the present invention was the one that was successfully chemically synthesized for the first time during the study of synthesis by the present inventors (Japanese Patent Application No. 3-23407), and the physical properties (melting points) of these compounds were , Vaporization temperature) proves this. In addition, the present invention is completed by further finding that the barium complex used in the present invention has a remarkable effect of lowering the vaporization temperature and improving the vaporization stability as compared with the existing complex. It has been reached.

Table 1 summarizes the vaporization temperature and vaporization stability of each complex. FIG. 1 is a diagram showing the results of examining the vaporization stability of three types of barium complexes, and shows the results obtained by a cycle test of isothermal thermogravimetric analysis. From this result, the vaporization stability when heated to each temperature can be known. In addition, the results show that the known compounds Ba (hfa) ₂ and Ba (fod) ₂ have a large change with time in vaporization.

[0019]

[Table 1]

Here, the contents of the abbreviations in parentheses in the abbreviations in the above table are collectively described below.

Hfa: hexafluoroacetylacetonato, (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato), pta: pivalyltrifluoromethylacetylacetonate, (1, 1,1-trifluoro-5,5-dimethyl-2,4-hexanedionato), ppm: pentafluoropivalyl methanate, (1,1,1,2,2-
Pentafluoro-6,6-dimethyl-3,5-heptanedionato), fod: dimethylheptafluorooctanedionato, (2,2
-Dimethyl-6,6,7,7,8,8,8-heptafluoro-
3,5-octanedione), dpm: dipivaloyl methanate, (2,2,6,6-tetramethyl-3,5-heptanedionate), ofhd: octafluorohexanedionate, (1,1,1, 5,5,
6,6,6-octafluoro-2,4-hexanedionato), dfhd: 1,1,1,5,5,6,6,7,7,7-decafluoro-2,4-heptanedionato, dfhpd : 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedionato, dfod: 1,1,1,2,2,6,6,7,7, 8,8,8-dodecafluoro-3,5
-Octandionato, tfnd: 1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluoro-4,6-nonandionato, hfdd: 1,1 , 1,2,2,3,3,7,7,8,8,9,9,10,10,10-hexadecafluoro-4,6-decandionate.

[0022]

EXAMPLES The production method of the present invention will be specifically described below with reference to examples.

FIG. 2 is a conceptual diagram showing the structure of the apparatus used in Examples 1 to 5 as an example of the apparatus used for carrying out the method for producing a fluoride thin film of the present invention. Here, reference numeral 1 denotes a quartz chamber as a reaction system, which is maintained at a pressure of 1 Torr by a rotary pump. In the chamber 1, a substrate 3 made of CaF ₂ is provided on the heater 2. Also, this chamber 1 has an inlet 1
The gas flow of the metal β-diketone complex and the fluorine-containing gas are introduced from a and 1b, respectively. Further, the configuration is such that a microwave (200 W) of 2.45 GHz is supplied from the magnetron tube 12 using the waveguide 11 to generate plasma.

[0024]

Example 1 In this example, 6
Zr (hfa) ₄ kept at 0 ° C, Ba (ofhd) ₂ kept at 190 ° C
[Bis (octafluorohexanedionato) barium],
La (ppm) ₃ [tris (pentafluorodimethylheptanedionato) lanthanum] kept at 170 ° C, kept at 60 ° C
Al (fod) ₃ and Na (ppm) kept at 170 ° C. were used. Also,
Ar was supplied as a carrier gas. That is, Zr is connected to the inlet 1a through the supply pipes 7a, 7b, 7c, 7d, and 7e.
The evaporators 8a, 8b, 8c, 8d and 8e filled with (hfa) ₄ , Ba (ofhd) ₂ , La (ppm) ₃ , Al (fod) ₃ and Na (ppm) are connected to each other. While heating the vessel, Ar
Is introduced into the chamber 1. In this case, the supply amount of each material can be adjusted by the flow rate of the Ar carrier gas.

A mixed gas of SF ₆ and oxygen selected as the fluorine-containing gas is supplied from the inlet 1b through the supply pipe 4, and the supply amount of these gases can be adjusted by the mass flow controller. ing.

The supply pipes 7a, 7b, 7c, 7d, 7e,
4 is a heat retaining heater 6a for suppressing gas condensation.
6b, 6c, 6d, 6e, 5 at 65 ° C, 200 respectively
The temperature is kept at 180 ℃, 180 ℃, 70 ℃ and 180 ℃.

In this embodiment, Zr (hfa) ₄ is 20 cc / min, B
a (ofhd) ₂ is 10cc / min, La (ppm) ₃ is 2cc / min, Al (fod) ₃
The 3cc / min, Na (ppm) is 10cc / min, SF ₆ is 20 cc / min, results oxygen which was carried out for 2 hours under the conditions of 5 cc / min, CaF ₂
A dense glass film of 500 μm thickness was deposited on the substrate. The composition of the obtained glass was 53ZrF ₄ -20BaF ₂ -4LaF ₃ ‐
3AlF ₃ -20NaF. As a result of measuring the distribution of each element in the thickness direction of this glass using XMA, the fluctuation was
It was 0.1 atomic% or less, and it was confirmed that the composition had excellent stability.

[0028]

Embodiments 2 to 5 Ba (dfhd) ₂ , Ba (dfod) ₂ , Ba (tfnd) ₂ and Ba (hd) shown in Table 1 were used instead of Ba (ofhd) ₂ in the embodiment 1.
fdd) ₂ and a fluoride thin film was produced in the same manner as in Example 1 except that the respective heating temperatures were applied. Also in this case, as in the case of Example 1, a glass film having excellent characteristics could be produced.

[0029]

Embodiment 6 FIG. 3 is a diagram showing a schematic configuration of an apparatus used when a barium fluoride thin film is manufactured in this embodiment. In the figure, bis is a raw material containing barium element.
(3H, 3H-decafluoroheptane-2,4-dionato) barium [Ba (dfhd) ₂ ] 25 is introduced as a carrier gas 33 into a bubbler container 26 in which a gas flow controller 27 controls the flow of argon gas. By doing so, an argon gas containing a required amount of the barium raw material is formed and supplied to the reaction vessel 1. In addition, if necessary, in order to promote the growth reaction, a predetermined amount of reactive gas, specifically, oxygen, boron trifluoride (B
F ₃ ), nitrogen trifluoride (NF ₃ ), sulfur hexafluoride (SF ₆ ), carbon tetrafluoride (CF ₄ ) and the like are supplied to the reaction vessel 1. In addition, various substrates such as silicon (111), silicon (110), sapphire, and quartz can be used as the substrate.

Here, when a silicon substrate (111 surface) is placed on a substrate holder 22 in a reaction vessel 21 and heated to a predetermined temperature, a chemical vapor reaction of the introduced barium complex causes the barium complex to be placed on the substrate 23. A BaF ₂ thin film is formed. More specifically, a 200 ° C. passed through a bubbler vessel 26 at 190 ° C.
Introducing cc / min of argon gas and 2000 cc / min of argon gas for acceleration into the reaction vessel 21 and simultaneously introducing 50 cc / min of oxygen gas into the reaction vessel 21 and heating the substrate to a temperature of 400 ° C. Thereby, a thin film is grown on the substrate. At this time, the pressure in the reaction vessel was controlled at 10 Torr, and the piping system was set at 20 Torr.
Control to 0 ° C and keep the chamber at 100 ° C.

The growth rate of the thin film obtained as described above was 14 μm per hour. Also, a good mirror surface was formed on the surface of this thin film, and the thin film was confirmed to be BaF ₂ by X-ray fluorescence analysis. Also, RHEE
D measurement confirmed that a single crystal thin film was formed. Further, the X-ray diffraction pattern is as shown in FIG.
Sharp diffraction peaks were observed at 24.8 degrees and 50.8 degrees.
11) It was confirmed that the thin film was oriented. Further, the half width determined from the X-ray rocking curve was 2 minutes. Further, the result of repeatedly performing the above-described thin film growth operation is as shown in FIG. 5, which is a good result showing that the thin film growth rate is almost constant and the reproducibility is constant. It showed the same characteristics as. Also, as a comparative example
The results when using Ba (dpm) ₂ compounds were also shown,
It can be seen that after several uses, the vaporizability is reduced and the growth rate is reduced.

[0032]

Example 7 Er is a β-diketone complex of erbium
(dpm) ₃ 28 but using bubbler container 29 filled with was prepared barium fluoride thin film in the same manner as in Example 6. Here, the temperature of the bubbler 29 was 200 ° C., and the flow rate of the argon gas was 5 cc / min. As a result, a barium fluoride thin film doped with 0.1% of erbium was obtained.
The thickness and crystal quality of the obtained thin film were the same as in Example 1.

[0033]

As described above, by using the method for producing a fluoride thin film according to the present invention as a barium element source, a specific barium compound having good vaporizability, thermal stability and reproducibility of thin film formation can be obtained. By using the method, it was possible to solve the problems of the prior art and to provide a method for producing an optically uniform fluoride thin film for an optical fiber or an optical element.

[Brief description of the drawings]

FIG. 1 is a diagram showing the cycle stability of vaporization of a barium complex used in a method for producing a fluoride thin film of the present invention and a conventionally known barium complex.

FIG. 2 is a configuration diagram showing an outline of an apparatus used in Examples 2 to 5.

FIG. 3 is a configuration diagram of an apparatus used in Examples 6 and 7.

FIG. 4 is an X-ray diffraction pattern of a thin film obtained by the method of the present invention.

FIG. 5 is a diagram showing the relationship between the growth rate of the barium fluoride thin film and the number of heating times of the barium fluoride thin films produced by the methods of Example 6 and Comparative Example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... Heating heater, 3 ... Substrate, 4 ... Reactive gas supply pipe, 5, 6 ... Heating heater for supply pipe, 7 ... Raw material supply pipe, 8 ... Evaporator, 9 ... Heater for raw material heating, 10 …
Raw material β-diketone complex, 21 reaction vessel, 22 heater, 23 substrate, 24 thermocouple, 25, 28 raw β-diketone complex, 26, 29 bubbler container, 27, 30, 31, 32 ... Gas flow controller, 33 ... Carrier gas, 34 ... Reactive gas.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-275726 (JP, A) JP-A-63-104312 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 19/00-19/32

Claims (3)

(57) [Claims] 1. A predetermined base material is placed in a gas phase reaction vessel, and a compound containing barium and other elements is introduced in a gas phase.
In a method in which the compound is decomposed in a plasma atmosphere to provide a fluoride thin film on the base material, a barium-β-diketone complex represented by the following formula as a compound containing barium (provided that (R ₁ , R ₂ ) is (CF ₃ , C ₂ F
_{5), (CF 3, C} 3 F 7), (C 2 F 5, C 2 F 5), (C 2 F 5, C 3 F 7), (C
_{3 F 7, C 3 F 7} ), (C 3 F 7, C 4 F 9) ones) method for producing a thin film of a fluoride which comprises using the. Embedded image 2. A predetermined base material is placed in a gas phase reaction vessel, and a compound containing barium and a reactive gas as necessary are introduced in a gas phase. In the method of providing a barium fluoride thin film, a barium-β-diketone complex represented by the following formula as a compound containing barium:
(However, the combination of (R ₁ , R ₂ ) in the following formula is (CF ₃ , C ₂ F ₅ ),
_{(CF 3, C 3 F 7} ), (C 2 F 5, C 2 F 5), (C 2 F 5, C 3 F 7), (C 3 F 7, C 3
F ₇ ) and (C ₃ F ₇ , C ₄ F ₉ )). Embedded image 3. A barium fluoride thin film produced by introducing a rare earth element β-diketone complex in the gas phase together with the barium-β-diketone complex to contain the rare earth element. For producing a barium fluoride thin film.